This 4-year study has 3 specific aims: (1) Examine patterns of longitudinal use of eye care diagnostic and therapeutic services for Medicare beneficiaries diagnosed with major eye diseases;(2) Analyze effects of the appropriate use of eye care services on vision outcomes and disease progression;and (3) Assess utilization, conformance with guidelines, and outcomes in addition to retinopathy for Medicare beneficiaries with diabetes mellitus (DM). Aim 1 investigates why some beneficiaries are persistent non-users of Medicare covered eye care services, effects of implementation of Medicare Part D on use of prescription drugs for glaucoma, and diffusion of new therapies for treatment of age-related macular degeneration. Aim 2 assesses effects of various eye care therapies on vision outcomes as well as complications of such therapies. Aim 3 investigates outcomes of DM with a focus on effects of adherence to care recommendations on health and longevity of persons diagnosed with DM. The study uses various econometric approaches (propensity score matching, instrumental variables, and control functions) to analyze national, longitudinal data bases: Medicare 5% claims data merged with vital statistics information from 1991-2010 (anticipated);Health and Retirement Survey data on Medicare beneficiaries merged with Medicare claims for 1993-2010 (anticipated);and Medicare Current Beneficiary Survey data also merged with administrative information from Medicare, 1991-2009 (anticipated).